FIGS. 1A and 1B depict conventional magnetic elements 10 and 10′. The conventional magnetic element 1 is a spin valve 10 and includes a conventional antiferromagnetic (AFM) layer 12, a conventional pinned layer 14, a conventional nonmagnetic spacer layer 16 and a conventional free layer 18. The conventional pinned layer 14 and the conventional free layer 18 are ferromagnetic. The conventional nonmagnetic spacer layer 16 is conductive. The AFM layer 12 is used to fix, or pin, the magnetization of the pinned layer 14 in a particular direction. The magnetization of the free layer 18 is free to rotate, typically in response to an external magnetic field. The conventional magnetic element 10′ depicted in FIG. 1B is a spin tunneling junction. Portions of the conventional spin tunneling junction 10′ are analogous to the conventional spin valve 10. Thus, the conventional magnetic element 10′ includes an AFM layer 12′, a conventional pinned layer 14′, a conventional insulating barrier layer 16′ and a conventional free layer 18′. The conventional barrier layer 16′ is thin enough for electrons to tunnel through in a conventional spin tunneling junction 10′.
Depending upon the orientations of the magnetizations of the conventional free layer 18/18′ and the conventional pinned layer 14/14′, respectively, the resistance of the conventional magnetic element 10/10′, respectively, changes. When the magnetizations of the conventional free layer 18/18′ and conventional pinned layer 14/14′ are parallel, the resistance of the conventional magnetic element /10′10 is low. When the magnetizations of the conventional free layer 18/18′ and the conventional pinned layer 14/14′ are antiparallel, the resistance of the conventional magnetic element 10/10′ is high.
To sense the resistance of the conventional magnetic element 10/10′, current is driven through the conventional magnetic element 10/10′. Current can be driven in one of two configurations, current in plane (“CIP”) and current perpendicular to the plane (“CPP”). In the CPP configuration, current is driven perpendicular to the layers of conventional magnetic element 10/10′ (up or down as seen in FIG. 1A or 1B).
One of ordinary skill in the art will readily recognize that the conventional magnetic elements 10 and 10′ may not function at higher memory cell densities. The conventional magnetic elements 10 and 10′ are typically written using an external magnetic field generated using current driven by components outside of the magnetic elements 10 and 10′. The magnetic field required to switch the magnetization of the free layer 18 or 18′ (switching field) is inversely proportional to the width of the conventional magnetic element 10 or 10′, respectively. Because the switching field is higher for smaller magnetic elements, the current required to generate the external magnetic field increases dramatically for higher magnetic memory cell densities. Consequently, cross talk and power consumption may increase. The driving circuits used to drive the current that generates the switching field could also increase in area and complexity. Further, the conventional write currents have to be large enough to switch a magnetic memory cell but not so large that the neighboring cells are inadvertently switched. This upper limit on the write current amplitude can lead to reliability issues because some cells are harder to switch than others (due to fabrication and material nonuniformity) and may fail to write consistently. Moreover, a higher write current is more likely to damage one or more of the layers of the magnetic elements 10 and 10′.
Accordingly, what is needed is a system and method for providing a magnetic memory element which can be used in a memory array of high density, low power consumption, low cross talk, and high reliability, while providing sufficient readout signal. The present invention addresses the need for such a magnetic memory element.